Such devices are employed for conducting analytical methods in order to qualitatively and quantitatively detect chemical parameters of liquid samples. The cuvette constitutes a liquid cell which accommodates the liquid sample to be examined. The sample is reacted with an adequate reagent in order to induce changes in the optical properties of the solution which may be measured photometrically. For this purpose, a radiation source is provided which produces visible light, infrared light or ultraviolet light, depending on the application. The cuvette displays an inlet window which is transparent to the employed excitation radiation for coupling in the excitation radiation which, after having passed through the sample volume, is coupled out via the outlet window. Hitherto, cuvette tests or equivalent tests have usually been performed using cuvettes with plane-parallel walls displaying incorporated inlet and outlet windows. Additionally, a lens system is provided in many cases in order to achieve an appropriate beam deflection or beam transformation on its way from the radiation source to the detector.
In the context of a transmitted light refractometer, the practice of arranging a hollow cuvette in the telecentric beam path of a monochromatic light source generating a divergent beam bundle, which is formed into a parallel beam bundle by means of a condenser and is focused, after having passed through the cuvette, onto a line-shaped sensor by means of a lens, has been known from DE 42 23 480 A1, for example. Such devices allow for precise deflection and imaging of the radiation to be examined, which is specifically adapted to the respective application. Disadvantageously, such imaging systems are very cost-intensive; furthermore, installing and adjusting the optical system is difficult and can often only be performed by a person with the necessary technical skill. Moreover, a great number of transition areas and interfaces are involved, causing imaging errors and performance loss.
In another context, DE 38 35 347 A1 describes a liquid cell having semicircular ends which is employed for laser intensification or phase conjugation by utilizing stimulated scattering processes.
Further, different types of turbidity sensors are known from DE 10 2006 052 887 A1, EP 0 404 258 A2 and DE 43 36 520 A1.